1. Technical Field
The invention relates generally to interlocking door skins and end caps, and a method of forming a door using these elements. More particularly, the invention relates to door skins having a plurality of interlocking tabs which function to secure the door skins as a unit and thereby define an upper opening and a lower opening for placing the end caps therein. Specifically, the invention relates to interlocking door skins which are secured together and formed to accept a top and bottom end cap which are formed by a separate locking clip element secured to a beam element.
2. Background Information
Doors in general, but industrial doors in particular, have suffered from a variety of defects which lead to dangerous operating conditions or unsatisfying build quality. Since wood is generally light and can be shaped and cut easily, wooden doors do not suffer from unsatisfying build quality. Nevertheless, wooden doors cannot withstand the harsh environments required of industrial applications and are therefore inappropriate.
Steel or metal doors, on the other hand, provide strength and the ability to withstand extreme environmental conditions. Due to the heavy material, the metal doors generally have a hollow cavity in order to substantially reduce the overall weight.
Traditionally, the metal door was manufactured with two door skins if the top and bottom pieces were manufactured integral to the respective door skins or four pieces if the top and bottom pieces were not integral to one of the door skins. One traditional method of manufacturing the door is to weld the pieces together at the seams. The welded door provides great resistance to the harsh environment and can generally withstand fires, but suffers from being a time consuming and costly procedure as well as unattractive.
The welded door is unattractive due to the welded seams which contain a variety of bumps and ridges from the welding process. Further, the welding process is generally unreliable and may cause material flexing and fitment issues due to the extreme heat required to weld the door together. Finally, the welded door is costly to produce because an acceptable door must be prepped for welding and then welded. Not only is welding expensive and time consuming, the unattractive seams that result must be sanded and polished to provide an acceptable finish. The sanding and polishing procedures are objectionable because they are both labor intensive and messy.
A second method of manufacturing a metal door is to use an adhesive. While the adhesive is easier, cheaper, and faster than welding, the adhesive is unable to endure the high heat of a fire and will melt, thereby posing a safety hazard. The process of adhering the doors skins with an adhesive still takes more time than is desired because the skins cannot be glued and then moved to the next processing station, but instead must remain untouched until the adhesive hardens. Further, if the doors are moved before the adhesive hardens, then the door skins will not be properly aligned and the door may have to be scraped, thereby increasing production costs. Thus there is a demonstrated need for an interlocking door assembly which is capable of being produced quickly and efficiently without welding and is able to withstand harsh environments as well as the extreme heat of a fire.
Furthermore, traditional monolithic end caps are difficult to manufacture due to the conflicting requirements of the end cap. The end cap should be manufactured from a durable material to conform to the overall strength and appearance of the metal door. Conversely, the end cap also requires the formation of intricate connecting elements thereon to connect the end cap to the door skins. Therefore, the main portion of the end cap should be formed from a durable material, yet the connecting should be formed from a more formable material, such as plastic. In addition, the end cap should also provide a thermal break in the metal material which forms the front and rear door surfaces. Metal material is desired due to its durability, yet the thermal conductivity of metal is such that thermal energy is easily transferred between the front and back door surfaces. For example, cold outdoor temperatures may be transferred to the interior facing door surface through the end caps and thereby act to cool the interior of the building, thus increasing heating costs for the building owner. As such, it is desirable that the end cap be formed of a material which has the property of low thermal conductivity, thus transfer of thermal energy through the door will be minimized. Therefore, there is a demonstrated need for a non-monolithic end cap which may be formed from two different materials, while also being formed of different materials from the front and rear door panels.